Method and apparatus for performing wt release procedure in wireless communication system

ABSTRACT

A method and apparatus for performing a wireless local area network (WLAN) termination (WT) release procedure in a wireless communication system is provided. For the eNodeB (eNB) initiated WT release procedure, the eNB transmits a WT Release Request message to a WT via a Xw interface. For the WT initiated WT release procedure, the eNB receives a WT Release Required message from a WT via a Xw interface, and transmits a WT Release Confirm message to the WT via the Xw interface. The WT is a logical node that terminates the Xw interface.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for performing a wireless localarea network (WLAN) termination (WT) release procedure and a WTreconfiguration notification procedure in a wireless communicationsystem.

Related Art

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3GPP LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Since Rel-8, 3GPP has standardized access network discovery andselection functions (ANDSF), which is for interworking between 3GPPaccess network and non-3GPP access network (e.g. wireless local areanetwork (WLAN)). The ANDSF may carry detection information of accessnetworks accessible in location of a user equipment (UE) (e.g., WLAN,WiMAX location information, etc.), inter-system mobility policies (ISMP)which is able to reflect operator's policies, and inter-system routingpolicy (ISRP). Based on the information described above, the UE maydetermine which Internet protocol (IP) traffic is transmitted throughwhich access network. The ISMP may include network selection rules forthe UE to select one active access network connection (e.g., WLAN or3GPP). The ISRP may include network selection rules for the UE to selectone or more potential active access network connection (e.g., both WLANand 3GPP). The ISRP may include multiple access connectivity (MAPCON),IP flow mobility (IFOM) and non-seamless WLAN offloading. Open mobilealliance (OMA) device management (DM) may be used for dynamic provisionbetween the ANDSF and the UE.

In addition to ANDSF, policy, i.e. radio access network (RAN) rule, hasbeen specified in Rel-12 for interworking between 3GPP access networkand non-3GPP access network (e.g. WLAN). By this policy, access networkselection and traffic steering between LTE and WLAN can be supported.That is, interworking between LTE and WLAN is moving in the direction ofincreasingly integrating LTE and WLAN. Accordingly, LTE-WLAN aggregationas well as LTE-WLAN interworking enhancements has been studied recently.But, there has been no agreement how to implement LTE-WLAN aggregation.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for performing awireless local area network (WLAN) termination (WT) release procedureand a WT reconfiguration notification procedure in a wirelesscommunication system. The present invention provides procedures andparameters for WLAN-LTE interworking and aggregation.

In an aspect, a method for performing, by an eNodeB (eNB), an eNBinitiated wireless local area network (WLAN) termination (WT) releaseprocedure in a wireless communication system is provided. The methodincludes transmitting a WT Release Request message to a WT via a Xwinterface. The WT is a logical node that terminates the Xw interface.

The WT Release Request message may request the WT to release allocatedWLAN resources. The WT Release Request message may include at least oneof an eNB Xw application protocol (AP) identifier (ID), a WT UE Xw APID, an E-UTRAN radio access bearer (E-RAB) ID and a downlink (DL) oruplink (UL) forwarding GPRS tunneling protocol (GTP) tunnel endpoint forE-RABs to be released or a cause to release.

The method may further include transmitting a radio resource control(RRC) connection reconfiguration message to a user equipment (UE). Themethod may further include receiving a RRC connection reconfigurationcomplete message from the UE.

In another aspect, a method for performing, by an eNodeB (eNB), awireless local area network (WLAN) termination (WT) initiated WT releaseprocedure in a wireless communication system is provided. The methodincludes receiving a WT Release Required message from a WT via a Xwinterface, and transmitting a WT Release Confirm message to the WT viathe Xw interface, as a response to the WT Release Required message. TheWT is a logical node that terminates the Xw interface.

The WT Release Required message may request release of allocated WLANresources. The WT Release Required message may include at least one ofan eNB Xw application protocol (AP) identifier (ID), a WT UE Xw AP ID ora cause to release.

The WT Release Confirm message may include at least one of an eNB AP ID,a WT UE Xw AP ID or an E-UTRAN radio access bearer (E-RAB) ID and adownlink (DL) or uplink (UL) forwarding GPRS tunneling protocol (GTP)tunnel endpoint for E-RABs to be released.

In another aspect, a method for performing, by an eNodeB (eNB), awireless local area network (WLAN) termination (WT) reconfigurationnotification procedure in a wireless communication system is provided.The method includes receiving a radio resource control (RRC) messagewhich indicates a WLAN connection failure from a user equipment (UE),and transmitting a failure cause corresponding the WLAN connectionfailure to a WT via a WT interface. The WT is a logical node thatterminates the Xw interface.

The failure cause may be transmitted via a WT Reconfiguration Completemessage. The failure cause may be transmitted via a WT Release Requestmessage. The failure cause may be transmitted immediately afterreceiving a WT Addition Request Acknowledge message from the WT.

Wireless local area network (WLAN) termination (WT)addition/modification/release procedure can be defined.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows LTE system architecture.

FIG. 2 shows a block diagram of architecture of a typical E-UTRAN and atypical EPC.

FIG. 3 shows a block diagram of a user plane protocol stack of an LTEsystem.

FIG. 4 shows a block diagram of a control plane protocol stack of an LTEsystem.

FIG. 5 shows an example of a physical channel structure.

FIG. 6 shows an example of 3GPP/WLAN interworking architecture.

FIG. 7 shows an example of an overall architecture for non-collocatedLWA scenario according to an embodiment of the present invention.

FIG. 8 shows an example of U-plane connectivity of eNB and WT for LWAaccording to an embodiment of the present invention.

FIG. 9 shows an example of C-plane connectivity of eNB and WT for LWAaccording to an embodiment of the present invention.

FIG. 10 shows an example of a WT addition procedure according to anembodiment of the present invention.

FIG. 11 shows another example of a WT addition procedure according to anembodiment of the present invention.

FIG. 12 shows an example of an eNB initiated WT modification procedureaccording to an embodiment of the present invention.

FIG. 13 shows another example of an eNB initiated WT modificationprocedure according to an embodiment of the present invention.

FIG. 14 shows an example of a WT initiated WT modification procedureaccording to an embodiment of the present invention.

FIG. 15 shows another example of a WT initiated WT modificationprocedure according to an embodiment of the present invention.

FIG. 16 shows an example of an eNB initiated WT release procedureaccording to an embodiment of the present invention.

FIG. 17 shows another example of an eNB initiated WT release procedureaccording to an embodiment of the present invention.

FIG. 18 shows an example of a WT initiated WT release procedureaccording to an embodiment of the present invention.

FIG. 19 shows another example of a WT initiated WT release procedureaccording to an embodiment of the present invention.

FIG. 20 shows an example of a WT reconfiguration complete procedureaccording to an embodiment of the present invention.

FIG. 21 shows an example of a WT release procedure according to anembodiment of the present invention.

FIG. 22 shows a communication system to implement an embodiment of thepresent invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is an evolution of IEEE 802.16e, and provides backwardcompatibility with an IEEE 802.16-based system. The UTRA is a part of auniversal mobile telecommunication system (UMTS). 3rd generationpartnership project (3GPP) long term evolution (LTE) is a part of anevolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA indownlink and uses the SC-FDMA in uplink. LTE-advance (LTE-A) is anevolution of the 3GPP LTE.

For clarity, the following description will focus on the LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 1 shows LTE system architecture. The communication network iswidely deployed to provide a variety of communication services such asvoice over internet protocol (VoIP) through IMS and packet data.

Referring to FIG. 1, the LTE system architecture includes one or moreuser equipment (UE; 10), an evolved-UMTS terrestrial radio accessnetwork (E-UTRAN) and an evolved packet core (EPC). The UE 10 refers toa communication equipment carried by a user. The UE 10 may be fixed ormobile, and may be referred to as another terminology, such as a mobilestation (MS), a user terminal (UT), a subscriber station (SS), awireless device, etc.

The E-UTRAN includes one or more evolved node-B (eNB) 20, and aplurality of UEs may be located in one cell. The eNB 20 provides an endpoint of a control plane and a user plane to the UE 10. The eNB 20 isgenerally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as a base station (BS), anaccess point, etc. One eNB 20 may be deployed per cell.

Hereinafter, a downlink (DL) denotes communication from the eNB 20 tothe UE 10, and an uplink (UL) denotes communication from the UE 10 tothe eNB 20. In the DL, a transmitter may be a part of the eNB 20, and areceiver may be a part of the UE 10. In the UL, the transmitter may be apart of the UE 10, and the receiver may be a part of the eNB 20.

The EPC includes a mobility management entity (MME) and a servinggateway (S-GW). The MME/S-GW 30 may be positioned at the end of thenetwork. For clarity, MME/S-GW 30 will be referred to herein simply as a“gateway,” but it is understood that this entity includes both the MMEand S-GW. A packet data network (PDN) gateway (P-GW) may be connected toan external network.

The MME provides various functions including non-access stratum (NAS)signaling to eNBs 20, NAS signaling security, access stratum (AS)security control, inter core network (CN) node signaling for mobilitybetween 3GPP access networks, idle mode UE reachability (includingcontrol and execution of paging retransmission), tracking area listmanagement (for UE in idle and active mode), P-GW and S-GW selection,MME selection for handovers with MME change, serving GPRS support node(SGSN) selection for handovers to 2G or 3G 3GPP access networks,roaming, authentication, bearer management functions including dedicatedbearer establishment, support for public warning system (PWS) (whichincludes earthquake and tsunami warning system (ETWS) and commercialmobile alert system (CMAS)) message transmission. The S-GW host providesassorted functions including per-user based packet filtering (by e.g.,deep packet inspection), lawful interception, UE Internet protocol (IP)address allocation, transport level packet marking in the DL, UL and DLservice level charging, gating and rate enforcement, DL rate enforcementbased on access point name aggregate maximum bit rate (APN-AMBR).

Interfaces for transmitting user traffic or control traffic may be used.The UE 10 is connected to the eNB 20 via a Uu interface. The eNBs 20 areconnected to each other via an X2 interface. Neighboring eNBs may have ameshed network structure that has the X2 interface. A plurality of nodesmay be connected between the eNB 20 and the gateway 30 via an S1interface.

FIG. 2 shows a block diagram of architecture of a typical E-UTRAN and atypical EPC. Referring to FIG. 2, the eNB 20 may perform functions ofselection for gateway 30, routing toward the gateway 30 during a radioresource control (RRC) activation, scheduling and transmitting of pagingmessages, scheduling and transmitting of broadcast channel (BCH)information, dynamic allocation of resources to the UEs 10 in both ULand DL, configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE_IDLE state management,ciphering of the user plane, SAE bearer control, and ciphering andintegrity protection of NAS signaling.

FIG. 3 shows a block diagram of a user plane protocol stack of an LTEsystem. FIG. 4 shows a block diagram of a control plane protocol stackof an LTE system. Layers of a radio interface protocol between the UEand the E-UTRAN may be classified into a first layer (L1), a secondlayer (L2), and a third layer (L3) based on the lower three layers ofthe open system interconnection (OSI) model that is well-known in thecommunication system.

A physical (PHY) layer belongs to the L1. The PHY layer provides ahigher layer with an information transfer service through a physicalchannel. The PHY layer is connected to a medium access control (MAC)layer, which is a higher layer of the PHY layer, through a transportchannel. A physical channel is mapped to the transport channel. Databetween the MAC layer and the PHY layer is transferred through thetransport channel. Between different PHY layers, i.e., between a PHYlayer of a transmission side and a PHY layer of a reception side, datais transferred via the physical channel.

A MAC layer, a radio link control (RLC) layer, and a packet dataconvergence protocol (PDCP) layer belong to the L2. The MAC layerprovides services to the RLC layer, which is a higher layer of the MAClayer, via a logical channel. The MAC layer provides data transferservices on logical channels. The RLC layer supports the transmission ofdata with reliability. Meanwhile, a function of the RLC layer may beimplemented with a functional block inside the MAC layer. In this case,the RLC layer may not exist. The PDCP layer provides a function ofheader compression function that reduces unnecessary control informationsuch that data being transmitted by employing IP packets, such as IPv4or IPv6, can be efficiently transmitted over a radio interface that hasa relatively small bandwidth.

A radio resource control (RRC) layer belongs to the L3. The RLC layer islocated at the lowest portion of the L3, and is only defined in thecontrol plane. The RRC layer controls logical channels, transportchannels, and physical channels in relation to the configuration,reconfiguration, and release of radio bearers (RBs). The RB signifies aservice provided the L2 for data transmission between the UE andE-UTRAN.

Referring to FIG. 3, the RLC and MAC layers (terminated in the eNB onthe network side) may perform functions such as scheduling, automaticrepeat request (ARQ), and hybrid ARQ (HARQ). The PDCP layer (terminatedin the eNB on the network side) may perform the user plane functionssuch as header compression, integrity protection, and ciphering.

Referring to FIG. 4, the RLC and MAC layers (terminated in the eNB onthe network side) may perform the same functions for the control plane.The RRC layer (terminated in the eNB on the network side) may performfunctions such as broadcasting, paging, RRC connection management, RBcontrol, mobility functions, and UE measurement reporting andcontrolling. The NAS control protocol (terminated in the MME of gatewayon the network side) may perform functions such as a SAE bearermanagement, authentication, LTE_IDLE mobility handling, pagingorigination in LTE_IDLE, and security control for the signaling betweenthe gateway and UE.

FIG. 5 shows an example of a physical channel structure. A physicalchannel transfers signaling and data between PHY layer of the UE and eNBwith a radio resource. A physical channel consists of a plurality ofsubframes in time domain and a plurality of subcarriers in frequencydomain. One subframe, which is 1 ms, consists of a plurality of symbolsin the time domain. Specific symbol(s) of the subframe, such as thefirst symbol of the subframe, may be used for a physical downlinkcontrol channel (PDCCH). The PDCCH carries dynamic allocated resources,such as a physical resource block (PRB) and modulation and coding scheme(MCS).

A DL transport channel includes a broadcast channel (BCH) used fortransmitting system information, a paging channel (PCH) used for paginga UE, a downlink shared channel (DL-SCH) used for transmitting usertraffic or control signals, a multicast channel (MCH) used for multicastor broadcast service transmission. The DL-SCH supports HARQ, dynamiclink adaptation by varying the modulation, coding and transmit power,and both dynamic and semi-static resource allocation. The DL-SCH alsomay enable broadcast in the entire cell and the use of beamforming.

A UL transport channel includes a random access channel (RACH) normallyused for initial access to a cell, a uplink shared channel (UL-SCH) fortransmitting user traffic or control signals, etc. The UL-SCH supportsHARQ and dynamic link adaptation by varying the transmit power andpotentially modulation and coding. The UL-SCH also may enable the use ofbeamforming.

The logical channels are classified into control channels fortransferring control plane information and traffic channels fortransferring user plane information, according to a type of transmittedinformation. That is, a set of logical channel types is defined fordifferent data transfer services offered by the MAC layer.

The control channels are used for transfer of control plane informationonly. The control channels provided by the MAC layer include a broadcastcontrol channel (BCCH), a paging control channel (PCCH), a commoncontrol channel (CCCH), a multicast control channel (MCCH) and adedicated control channel (DCCH). The BCCH is a downlink channel forbroadcasting system control information. The PCCH is a downlink channelthat transfers paging information and is used when the network does notknow the location cell of a UE. The CCCH is used by UEs having no RRCconnection with the network. The MCCH is a point-to-multipoint downlinkchannel used for transmitting multimedia broadcast multicast services(MBMS) control information from the network to a UE. The DCCH is apoint-to-point bi-directional channel used by UEs having an RRCconnection that transmits dedicated control information between a UE andthe network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by the MAC layer include a dedicatedtraffic channel (DTCH) and a multicast traffic channel (MTCH). The DTCHis a point-to-point channel, dedicated to one UE for the transfer ofuser information and can exist in both uplink and downlink. The MTCH isa point-to-multipoint downlink channel for transmitting traffic datafrom the network to the UE.

Uplink connections between logical channels and transport channelsinclude the DCCH that can be mapped to the UL-SCH, the DTCH that can bemapped to the UL-SCH and the CCCH that can be mapped to the UL-SCH.Downlink connections between logical channels and transport channelsinclude the BCCH that can be mapped to the BCH or DL-SCH, the PCCH thatcan be mapped to the PCH, the DCCH that can be mapped to the DL-SCH, andthe DTCH that can be mapped to the DL-SCH, the MCCH that can be mappedto the MCH, and the MTCH that can be mapped to the MCH.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. The RRC state may be dividedinto two different states such as an RRC idle state (RRC_IDLE) and anRRC connected state (RRC_CONNECTED). In RRC_IDLE, the UE may receivebroadcasts of system information and paging information while the UEspecifies a discontinuous reception (DRX) configured by NAS, and the UEhas been allocated an identification (ID) which uniquely identifies theUE in a tracking area and may perform public land mobile network (PLMN)selection and cell re-selection. Also, in RRC_IDLE, no RRC context isstored in the eNB.

In RRC_CONNECTED, the UE has an E-UTRAN RRC connection and a context inthe E-UTRAN, such that transmitting and/or receiving data to/from theeNB becomes possible. Also, the UE can report channel qualityinformation and feedback information to the eNB. In RRC_CONNECTED, theE-UTRAN knows the cell to which the UE belongs. Therefore, the networkcan transmit and/or receive data to/from UE, the network can controlmobility (handover and inter-radio access technologies (RAT) cell changeorder to GSM EDGE radio access network (GERAN) with network assistedcell change (NACC)) of the UE, and the network can perform cellmeasurements for a neighboring cell.

In RRC_IDLE, the UE specifies the paging DRX cycle. Specifically, the UEmonitors a paging signal at a specific paging occasion of every UEspecific paging DRX cycle. The paging occasion is a time interval duringwhich a paging signal is transmitted. The UE has its own pagingoccasion. A paging message is transmitted over all cells belonging tothe same tracking area. If the UE moves from one tracking area (TA) toanother TA, the UE will send a tracking area update (TAU) message to thenetwork to update its location.

In Rel-12, 3GPP/WLAN interworking for access network selection andtraffic steering was introduced. In order to performing traffic steeringfrom LTE to WLAN or vice versa, UE decision based solution was definedin Rel-12. That is, the eNB may just provide radio access network (RAN)rule to the UE, and the UE may decide which access network to select orto which access network traffic is to be steered, based on the receivedRAN Rule and its information.

FIG. 6 shows an example of 3GPP/WLAN interworking architecture.Referring to FIG. 6, the UE is connected to the P-GW via the eNB in 3GPPaccess network, via enhanced packet data gateway (ePDG) in non-3GPPaccess network, i.e. WLAN. The eNB may provide RAN rule to the UE. TheUE may determine access network to which traffic is to be steeredbetween 3GPP and WLAN, based on the RAN rule and information that the UEhas.

3GPP/WLAN interworking for access network selection and traffic steeringintroduced in Rel-12 is different from legacy mobility procedure (e.g.S1/X2 handover procedure), in which the eNB always makes the decision.Accordingly, 3GPP/WLAN interworking controlled by the eNB has beendiscussed from Rel-13. Currently, there is no procedure for 3GPP/WLANinterworking controlled by the eNB.

3GPP/WLAN radio interworking Rel-12 solution may enhance core network(CN)-based WLAN offload by improving user quality of experience (QoE)and network utilization and providing more control to operators. Theseimprovements can be further enhanced by LTE-WLAN aggregation and furtherLTE-WLAN interworking enhancement relevant to both co-located andnon-co-located deployment scenarios. The benefits of the LTE-WLANaggregation are:

(1) WLAN access network becomes transparent to CN in the sense that itshould not require WLAN-specific CN nodes and CN interfaces. Thisprovides the operator unified control and management of both 3GPP andWLAN networks as opposed to separately managing them.

(2) Aggregation and tight integration at radio level allows forreal-time channel and load aware radio resource management across WLANand LTE to provide significant capacity and QoE improvements.

(3) The reliable LTE network can be used as a control and mobilityanchor to provide QoE improvements, minimize service interruption, andincrease operator control.

(4) No new WLAN-related CN signaling is needed, thus reducing CN load.

Accordingly, E-UTRAN may support LTE-WLAN aggregation (LWA) operationwhereby a UE in RRC_CONNECTED is configured by the eNB to utilize radioresources of LTE and WLAN. Two scenarios may be supported depending onthe backhaul connection between LTE and WLAN, one of which isnon-collocated LWA scenario for a non-ideal backhaul, and the other iscollocated LWA scenario for an ideal/internal backhaul.

FIG. 7 shows an example of an overall architecture for non-collocatedLWA scenario according to an embodiment of the present invention.Referring to FIG. 7, WLAN termination (WT) terminates the Xw interfacefor WLAN. The WT may be a logical node that terminates the Xw interfaceon the WLAN side, and 3GPP may not specify where it is implemented.

In LWA, the radio protocol architecture that a particular bearer usesmay depend on the LWA backhaul scenario and how the bearer is set up.Two bearer types may exist for LWA, one of which is split LWA bearer andthe other is switched LWA bearer. The split LWA bearer is a bearer whoseradio protocols are located in both the eNB and the WLAN to use both eNBand WLAN radio resources in LWA. The switched LWA bearer is a bearerwhose radio protocols are located in both the eNB and the WLAN but usesWLAN radio resources only in LWA.

In the non-collocated LWA scenario, the eNB may be connected to one ormore WTs via an Xw interface. In the collocated LWA scenario, theinterface between LTE and WLAN may be up to implementation. For LWA, theonly required interfaces to the core network are S1-U and S1-MME whichare terminated at the eNB. No core network interface may be required forthe WLAN.

FIG. 8 shows an example of U-plane connectivity of eNB and WT for LWAaccording to an embodiment of the present invention. Referring to FIG.8, in the non-collocated LWA scenario, the S1-U is terminated at theeNB, and the eNB and the WT are interconnected via Xw user planeinterface (Xw-U). The Xw-U interface may support flow control based onfeedback from WT. The flow control function may be applied in the DLwhen an E-UTRAN radio access bearer (E-RAB) is mapped onto an LWAbearer, i.e. the flow control information may be provided by the WT tothe eNB for the eNB to control the DL user data flow to the WT for theLWA bearer. The Xw-U interface may be used to deliver LWA protocol dataunits (PDUs) between eNB and WT. For LWA, the S1-U may terminate in theeNB and, if Xw-U user data bearers are associated with E-RABs for whichthe LWA bearer option is configured, the user plane data may betransferred from eNB to WT using the Xw-U interface.

FIG. 9 shows an example of C-plane connectivity of eNB and WT for LWAaccording to an embodiment of the present invention. Referring to FIG.9, in the non-collocated LWA scenario, the S1-MME is terminated at theeNB, and the eNB and the WT are interconnected via Xw control planeinterface (Xw-C). The application layer signaling protocol may bereferred to as Xw-AP (Xw application protocol). The Xw-AP protocolsupports the following functions:

-   -   Transfer of WLAN metrics (e.g. bss load) from WT to eNB;    -   Support of LWA for UE in ECM-CONNECTED: Establishment,        modification and release of a UE context at the WT, and/or        control of user plane tunnels between eNB and WT for a specific        UE for LWA bearers;    -   General Xw management and error handling functions: Error        indication; setting up the Xw; resetting the Xw; updating the WT        configuration data;

eNB-WT control plane signaling for LWA may be performed by means of Xw-Cinterface signaling. There may be only one S1-MME connection per LWA UEbetween the eNB and the MME. Respective coordination between eNB and WTmay be performed by means of Xw interface signaling.

Hereinafter, procedures for both 3GPP-WLAN interworking and integrationaccording to embodiments of the present invention are described. Thefollowing procedures may include procedures for different situations,e.g. procedures for WT addition, procedures for WT modification, orprocedures for WT release. Further, the following procedures may bebased on an interface between eNB and WT, e.g. Xw interface describedabove or another interface. Further, WT and WLAN may denote to the samemeaning in the description below, and accordingly, may be replaced witheach other in the description below.

(1) WT Addition Procedure

FIG. 10 shows an example of a WT addition procedure according to anembodiment of the present invention. The WT addition procedure may beinitiated by the eNB and may be used to establish a UE context at the WTin order to provide WLAN resources to the UE. That is, the WT additionprocedure may be used to request the WT to establish LWA bearer(s) for aspecific UE.

In step S100, the eNB transmits a WT Addition Request message to the WT.By this step, the eNB may decide to request the WT to allocate WLANresources for specific E-RABs, indicating E-RAB characteristics. The WTAddition Request message may include the LWA bearer(s) for the specificUE. More specifically, the WT Addition Request message may include atleast one of 1) eNB Xw AP ID to identify the UE, 2) E-RAB ID, E-RABquality of service (QoS) for E-RABs to be added, 3) eNB GPRS tunnelingprotocol (GTP) tunnel endpoint (for UL PDU delivery) for E-RABs to beadded, 4) data forwarding indication, 5) security key, or 6) selectedWLAN identifier (e.g. service set ID (SSID), basic service set ID(BSSID), homogeneous extended service set ID (HESSID)). For LTE-WLANintegration, all pieces of information described above may be includedin the WT Addition Request message. For LTE-WLAN interworking, 1), 2)and 6) among pieces of information described above may be included inthe WT Addition Request message. The WT may reject the request with acause value, e.g. no radio resource available.

Table 1 shows an example of the WT Addition Request message. Thismessage is sent by the eNB to the WT to request the preparation ofresources for LTE-WLAN aggregation for a specific UE.

TABLE 1 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the eNBUE Identity M 9.2.16 YES reject WLAN Security O 9.2.27 YES rejectInformation Serving PLMN O PLMN The serving YES ignore Identity 9.2.3PLMN for the UE. E-RABs To Be 1 YES reject Added List >E-RABs To Be 1 .. . EACH reject Added Item <maxnoof Bearers> >>E-RAB ID M 9.2.18 —— >>E-RAB Level M 9.2.19 Includes necessary — — QoS Parameters QoSparameters >> eNB GTP M GTP Tunnel Endpoint of — — Tunnel EndpointEndpoint the Xw transport 9.2.22 bearer at the eNB Mobility Set M 9.2.28YES reject

Referring to Table 1, the WT Addition Request message includes eNB Xw APID (“eNB UE XwAP ID”), E-RAB ID, E-RAB QoS and eNB GTP tunnel endpoint(in “E-RABs To Be Added Item”), security key (“WLAN SecurityInformation”) and selected WLAN identifier (“Mobility Set”).

If the WT is able to admit the full or partial WLAN resource request, instep S101, the WT transmits a WT Addition Request Acknowledge message tothe eNB. That is, in case one or more GTP tunnel(s) at the WT has beenestablished successfully, the WT may respond with the WT AdditionRequest Acknowledge message, which includes successfully established andfailed to be established bearers for LWA. More specifically, the WTAddition Request Acknowledge message may include at least one of 1) eNBXw AP ID, WT Xw AP ID to identify the UE, 2) admitted E-RAB IDs, 3) WTGTP tunnel endpoint (for DL PDU delivery) for admitted E-RABs, 4) notadmitted E-RAB IDs, 5) data forwarding tunnel IDs (TEIDs), or 6)parameters need to be delivered to UE through eNB (e.g. beacon). ForLTE-WLAN integration, all pieces of information described above may beincluded in the WT Addition Request Acknowledge message. For LTE-WLANinterworking, 1), 2), 4) and 6) among pieces of information describedabove may be included in the WT Addition Request Acknowledge message.

Table 2 shows an example of the WT Addition Request Acknowledge message.This message is sent by the WT to confirm the eNB about the WT additionpreparation.

TABLE 2 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the WT E-RABsAdmitted 1 YES ignore To Be Added List >E-RABs 1 . . . EACH ignoreAdmitted To Be <maxnoof Added Item Bearers> >>E-RAB ID M 9.2.18 — — >>WTGTP M GTP Tunnel Endpoint of — — Tunnel Endpoint Endpoint the Xwtransport 9.2.22 bearer at the WT. E-RABs Not O E-RAB List A value forE- YES ignore Admitted List 9.2.23 RAB ID shall only be present once inE-RABs Admitted List IE and in E-RABs Not Admitted List IE. CriticalityO 9.2.5 YES ignore Diagnostics

Referring to Table 2, the WT Addition Request Acknowledge messageincludes eNB Xw AP ID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP ID”),admitted E-RAB IDs and WT GTP tunnel endpoint (in “E-RABs Admitted To BeAdded Item”), and not admitted E-RAB IDs (“E-RABs Not Admitted List”).

In step S102, the eNB transmits the RRCConnectionReconfiguration messageto the UE with necessary information from the WT and the information ofthe eNB. The RRCConnectionReconfiguration message may include the newradio resource configuration. In step S103, the UE applies the newconfiguration and replies with the RRCConnectionReconfigurationCompletemessage to the eNB. The UE starts using the new LWA configuration andperforms WLAN association.

In step S104, the eNB may transmit a WLAN Reconfiguration Completemessage to the WT to indicate the status to the WT. In step S105, the WTtransmits a WT Association Confirmation message to the eNB.

Thereafter, for data forwarding or data transmission, the eNB maytransmit the SN Status Transfer message to the WT, and data may beforwarded from the S-GW to the WT via the eNB. These steps may beperformed for LTE-WLAN integration. Or, to indicate the offloadingbehavior to the MME, the eNB may perform the path update proceduretowards the MME by indicating the E-RABs to be offloaded to the WT. TheMME may transmit the Path Update Acknowledge message to the eNB. Thesesteps may be performed for LTE-WLAN interworking. It is described aboveas if procedures for LTE-WLAN aggregation and procedures for LTE-WLANinterworking are separate from each other. However, it does not have tobe separate from each other.

FIG. 11 shows another example of a WT addition procedure according to anembodiment of the present invention.

In step S110, the eNB transmits the WT Addition Request message to theWT. Step S110 may correspond to step S100 of FIG. 10. The WT AdditionRequest message may follow Table 1 described above.

In step S111, the WT transmits the WT Addition Request Acknowledgemessage to the eNB. Step S111 may correspond to step S101 of FIG. 10.The WT Addition Request Acknowledge message may follow Table 2 describedabove.

(2) eNB Initiated WT Modification Procedure

FIG. 12 shows an example of an eNB initiated WT modification procedureaccording to an embodiment of the present invention. The eNB initiatedWT modification procedure may be used to modify, establish or releasebearer contexts or to modify other properties of the UE context withinthe same WT. That is, the eNB initiated WT modification procedure may beused to request the WT to modify LWA bearer(s) for a specific UE at theWT. The WT modification procedure may not necessarily need to involvesignaling towards the UE.

In step S200, the eNB transmits a WT Modification Request message to theWT. By this step, the eNB may request the WT to modify the WLANresources for specific E-RABs. More specifically, the WT ModificationRequest message may include at least one of 1) eNB Xw AP ID, WT Xw AP IDto identify the UE, 2) E-RAB ID, E-RAB QoS for E-RABs to beadded/modified/released, 3) eNB GTP tunnel endpoint (for UL PDUdelivery) for E-RABs to be added/modified/released, 4) data forwardingindication (DL/UL forwarding GTP tunnel endpoint), 5) security key, 6)selected WLAN identifier (e.g. SSID, BSSID, HESSID), 7) cause to modify,or 8) WT change indication. For LTE-WLAN integration, all pieces ofinformation described above may be included in the WT ModificationRequest message. For LTE-WLAN interworking, 1), 2), 6), 7) and 8) amongpieces of information described above may be included in the WTModification Request message.

Table 3 shows an example of the WT Modification Request message. Thismessage is sent by the eNB to the WT to request the preparation tomodify WT resources for a specific UE.

TABLE 3 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the WT Cause M9.2.4 YES ignore Serving PLMN O PLMN The serving YES ignore Identity9.2.3 PLMN for the UE. UE Context 0 . . . 1 YES reject Information >WLANSecurity O 9.2.27 Information >E-RABs To Be 0 . . . 1 — — AddedList >>E-RABs To Be 1 . . . EACH ignore Added Item <maxnoofBearers> >>>E-RAB ID M 9.2.18 — — >>>E-RAB M 9.2.19 Includes necessary —— Level QoS QoS parameters Parameters >>> eNB GTP M GTP Tunnel Endpointof — — Tunnel Endpoint Endpoint the Xw transport 9.2.22 bearer at theeNB >E-RABs To Be 0 . . . 1 — — Modified List >>E-RABs To Be 1 . . .EACH ignore Modified Item <maxnoof Bearers> >>>E-RAB ID M 9.2.18 —— >>>E-RAB O 9.2.19 Includes QoS — — Level QoS parameters to Parametersbe modified >>> eNB GTP O GTP Tunnel Endpoint of — — Tunnel EndpointEndpoint the Xw transport 9.2.22 bearer at the eNB >E-RABs To Be 0 . . .1 — — Released List >>E-RABs To Be 1 . . . EACH ignore Released Item<maxnoof Bearers> >>>E-RAB ID M 9.2.18 — — >>>DL O GTP Tunnel Identifiesthe — — Forwarding Endpoint Xw transport GTP Tunnel 9.2.22 bearer usedEndpoint for forwarding of DL PDUs Mobility Set O 9.2.28 YES reject

Referring to Table 3, the WT Modification Request message includes eNBXw AP ID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP IE”), 2) E-RAB ID,E-RAB QoS and eNB GTP tunnel endpoint for E-RABs to be added/modified(in “E-RABs To Be Added Item”, “E-RABs To Be Modified Item”,), dataforwarding indication for E-RABs to be released (in “E-RABs To BeRelease Item”), security key (“WLAN Security Information”), selectedWLAN identifier (“Mobility Set”) and cause to modify (“Cause”).

If the WT accepts the request, it applies the modified WLAN resourceconfiguration, and in step S201, the WT transmits a WT ModificationRequest Acknowledge message to the eNB. That is, in case resourcemodification at the WT has been performed successfully, the WT respondswith the WT Modification Request Acknowledge message. More specifically,the WT Modification Request Acknowledge message may include at least oneof 1) eNB Xw AP ID, WT Xw AP ID to identify the UE, 2) admitted E-RABIDs for E-RABs to be added/modified/released, 3) WT GTP tunnel endpoint(for DL PDU delivery) for admitted E-RABs, 4) not admitted E-RAB IDs, 5)data forwarding TEIDs, or 6) parameters need to be delivered to UEthrough eNB (e.g. beacon). For LTE-WLAN integration, all pieces ofinformation described above may be included in the WT ModificationRequest Acknowledge message. For LTE-WLAN interworking, 1), 2), 4) and6) among pieces of information described above may be included in the WTModification Request Acknowledge message.

Table 4 shows an example of the WT Modification Request Acknowledgemessage. This message is sent by the WT to confirm the eNB about the WTaddition preparation.

TABLE 4 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the WT E-RABsAdmitted 0 . . . 1 YES ignore List >E-RABs 0 . . . 1 — — Admitted To BeAdded List >>E-RABs 1 . . . EACH ignore Admitted To Be <maxnoof AddedItem Bearers> >>>E-RAB ID M 9.2.18 — — >>>WT GTP M GTP Tunnel Endpointof — — Tunnel Endpoint Endpoint the Xw transport 9.2.22 bearer at theWT. >E-RABs 0 . . . 1 — — Admitted To Be Modified List >>E-RABs 1 . . .EACH ignore Admitted To Be <maxnoof Modified Item Bearers> >>>E-RAB ID M9.2.18 — — >>>WT GTP O GTP Tunnel Endpoint of — — Tunnel EndpointEndpoint the Xw transport 9.2.22 bearer at the WT. >E-RABs 0 . . . 1 — —Admitted To Be Released List >>E-RABs 1 . . . EACH ignore Admitted To Be<maxnoof Released Item Bearers> >>>E-RAB ID M 9.2.18 — — E-RABs Not OE-RAB List A value for E- YES ignore Admitted List 9.2.23 RAB ID shallonly be present once in E-RABs Admitted List IE and in E- RABs NotAdmitted List IE. Criticality O 9.2.5 YES ignore Diagnostics

Referring to Table 4, the WT Modification Request Acknowledge messageincludes eNB Xw AP ID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP ID”),admitted E-RAB IDs and WT GTP tunnel endpoint for E-RABs to beadded/modified/released (in “E-RABs Admitted To Be Added Item”), and notadmitted E-RAB IDs (“E-RABs Not Admitted List”).

If the modification requires RRC configuration, in step S202, the eNBmay transmit the RRCConnectionReconfiguration message to the UEincluding the new WLAN radio resource configuration. In step S203, theUE may apply the new RRC configuration and may reply withRRCConnectionReconfigurationComplete message to the eNB. The UE startsusing the new LWA configuration. In step S204, the eNB may transmit aWLAN Reconfiguration Complete message to the WT to indicate the statusto the WT.

Thereafter, the eNB may transmit the SN Status Transfer message to theWT, and data may be forwarded from the S-GW to the WT via the eNB. Thesesteps may be performed for LTE-WLAN integration. Or, the eNB may performthe path update procedure towards the MME by indicating the E-RABs to beoffloaded to the WT. The MME may transmit the Path Update Acknowledgemessage to the eNB. These steps may be performed for LTE-WLANinterworking. It is described above as if procedures for LTE-WLANaggregation and procedures for LTE-WLAN interworking are separate fromeach other. However, it does not have to be separate from each other.

FIG. 13 shows another example of an eNB initiated WT modificationprocedure according to an embodiment of the present invention.

In step S210, the eNB transmits the WT Modification Request message tothe WT. Step S210 may correspond to step S200 of FIG. 12. The WTModification Request message may follow Table 3 described above.

In step S211, the WT transmits the WT Modification Request Acknowledgemessage to the eNB. Step S211 may correspond to step S201 of FIG. 12.The WT Modification Request Acknowledge message may follow Table 4described above.

(3) WT Initiated WT Modification Procedure

FIG. 14 shows an example of a WT initiated WT modification procedureaccording to an embodiment of the present invention. The WT initiated WTmodification procedure may be used to modify, establish or releasebearer contexts or to modify other properties of the UE context withinthe same WT. That is, the WT initiated WT modification procedure may beused to request the eNB to release LWA bearer(s) for a specific UE. Forexample, when the load situation of WLAN is not good, the WT may beallowed to trigger the modification for added bearers, i.e. to requestto release some of them. In addition, the WT may be allowed to triggerto the parameters change, e.g. mobility set change of SSID serving theUE, etc. or security parameters. The WT modification procedure may notnecessarily need to involve signaling towards the UE.

In step S300, the WT transmits a WT Modification Required message to theeNB. By this step, the WT may request the release of the allocated WLANresources for specific E-RABs. More specifically, the WT ModificationRequired message may include at least one of 1) eNB Xw AP ID, WT Xw APID to identify the UE, 2) E-RAB ID and cause for E-RABs to be released,3) cause to modify, or 4) WT change indication. The WT change indicationmay include at least one of security key/parameters change, or mobilityset change (WLAN IDs, e.g. SSID/BSSID).

Table 5 shows an example of the WT Modification Required message. Thismessage is sent by the WT to the eNB to request the release ormodification of LWA bearers for a specific UE.

TABLE 5 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the WT Cause M9.2.4 YES ignore E-RABs To Be 0 . . . 1 YES ignore Released List >E-RABsTo Be 1 . . . EACH ignore Released Item <maxnoof Bearers> >>E-RAB ID M9.2.18 — — >>Cause M 9.2.4 — — E-RABs To Be 0 . . . 1 — — ModifiedList >E-RABs To Be 1 . . . EACH ignore Modified Item <maxnoofBearers> >>E-RAB ID M 9.2.18 — — >>WT GTP O GTP Tunnel Endpoint of — —Tunnel Endpoint Endpoint the Xw transport 9.2.22 bearer at the WT

Referring to Table 5, the WT Modification Required message includes eNBXw AP ID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP ID”), E-RAB ID andcause for E-RABs to be released (in “E-RABs To Be Released Item”) andcause to modify (“Cause”).

Further, for at least one of data forwarding indication, security key orWT change indication, in step S301, the eNB may transmit the WTModification Request message to the WT, and in step S302, the WT maytransmit the WT Modification Request Acknowledge message to the eNB.

If the eNB decides to follow the WT request, in step S303, the eNBtransmits a WT Modification Confirm message to the WT. Morespecifically, the WT Modification Request Acknowledge message mayinclude at least one of 1) eNB Xw AP ID, WT Xw AP ID to identify the UE,or 2) parameters need to be delivered to the WT.

Table 6 shows an example of the WT Modification Confirm message. Thismessage is sent by the eNB to inform the WT that the WT initiated WTmodification was successful.

TABLE 6 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the WT E-RABsConfirmed 0 . . . 1 — — To Be Released List >E-RABs 1 . . . EACH ignoreConfirmed To Be <maxnoof Released Item Bearers> >>E-RAB ID M 9.2.18 —— >>DL O GTP Tunnel Identifies the — — Forwarding GTP Endpoint Xwtransport Tunnel Endpoint 9.2.22 bearer used for forwarding of DL PDUsE-RABs Confirmed 0 . . . 1 — — To Be Modified List >E-RABs 1 . . . EACHignore Confirmed To Be <maxnoof Modified Item Bearers> >>E-RAB ID M9.2.18 — — Criticality O 9.2.5 YES ignore Diagnostics

Referring to Table 5, the WT Modification Confirm message includes eNBXw AP ID (“eNB UE XwAP ID”) and WT Xw AP ID (“WT UE XwAP ID”).

If the modification requires RRC configuration, in step S304, the eNBmay transmit the RRCConnectionReconfiguration message to the UEincluding the new WLAN radio resource configuration. In step S305, theUE may apply the new RRC configuration and may reply withRRCConnectionReconfigurationComplete message to the eNB. The UE startsusing the new LWA configuration.

Thereafter, the eNB may transmit the SN Status Transfer message to theWT, and data may be forwarded from the S-GW to the WT via the eNB. Thesesteps may be performed for LTE-WLAN integration. Or, the eNB may performthe path update procedure towards the MME by indicating the E-RABs to beoffloaded to the WT. The MME may transmit the Path Update Acknowledgemessage to the eNB. These steps may be performed for LTE-WLANinterworking. It is described above as if procedures for LTE-WLANaggregation and procedures for LTE-WLAN interworking are separate fromeach other. However, it does not have to be separate from each other.

FIG. 15 shows another example of a WT initiated WT modificationprocedure according to an embodiment of the present invention.

In step S310, the eNB transmits the WT Modification Required message tothe WT. Step S310 may correspond to step S300 of FIG. 14. The WTModification Required message may follow Table 5 described above.

In step S311, the WT transmits the WT Modification Confirm message tothe eNB. Step S311 may correspond to step S303 of FIG. 14. The WTModification Confirm message may follow Table 6 described above.

(4) eNB Initiated WT Release Procedure

FIG. 16 shows an example of an eNB initiated WT release procedureaccording to an embodiment of the present invention. The eNB initiatedWT release procedure may be used to initiate the release of the UEcontext at the WT. The recipient node of this request may not reject.The eNB initiated WT release procedure may not necessarily need toinvolve signaling towards the UE.

In step S400, the eNB transmits a WT Release Request message to the WT.By this step, the eNB may request the WT to release the allocated WLANresources. More specifically, the WT Release Request message may includeat least one of 1) eNB Xw AP ID, WT Xw AP ID to identify the UE, 2)E-RAB ID and DL/UL forwarding GTP tunnel endpoint for E-RABs to bereleased, or 3) cause to release. The WT initiates release of allallocated WLAN resources.

Table 7 shows an example of the WT Release Request message. This messageis sent by the eNB to the WT to request the release of resources.

TABLE 7 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESignore eNB UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the WT Cause O9.2.4 YES ignore E-RABs To Be 0 . . . 1 YES ignore Released List >E-RABs To Be 1 . . . EACH ignore Released Item <maxnoof Bearers> >>E-RABID M 9.2.18 — — >>DL O GTP Tunnel Identifies the — — Forwarding GTPEndpoint Xw transport Tunnel Endpoint 9.2.22 bearer. used for forwardingof DL PDUs

Referring to Table 7, the WT Release Request message includes eNB Xw APID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP ID”), E-RAB ID and DL/ULforwarding GTP tunnel endpoint for E-RABs to be released (in “E-RABs ToBe Release Item”), and cause to release (“Cause”).

If required, in step S401, the eNB may transmit theRRCConnectionReconfiguration message to the UE indicating the release ofWLAN radio resource configuration. In step S402, the UE may reply withRRCConnectionReconfigurationComplete message to the eNB. The UE mayreleases the LWA configuration towards the assigned WLAN resources. TheeNB transmits the UE Context Release message to the WT.

Thereafter, the eNB may transmit the SN Status Transfer message to theWT, and data may be forwarded from the WT to the eNB. These steps may beperformed for LTE-WLAN integration. Or, the eNB may perform the pathupdate procedure towards the MME by indicating the E-RABs to beoffloaded to the WT. The MME may transmit the Path Update Acknowledgemessage to the eNB. These steps may be performed for LTE-WLANinterworking. It is described above as if procedures for LTE-WLANaggregation and procedures for LTE-WLAN interworking are separate fromeach other. However, it does not have to be separate from each other.

FIG. 17 shows another example of an eNB initiated WT release procedureaccording to an embodiment of the present invention.

In step S410, the eNB transmits the WT Release Request message to theWT. Step S410 may correspond to step S400 of FIG. 16. The WT ReleaseRequest message may follow Table 7 described above.

(5) WT Initiated WT Release Procedure

FIG. 18 shows an example of a WT initiated WT release procedureaccording to an embodiment of the present invention. The WT initiated WTrelease procedure may be used to initiate the release of the UE contextat the WT. The recipient node of this request may not reject. The eNBinitiated WT release procedure may not necessarily need to involvesignaling towards the UE.

In step S500, the WT transmits a WT Release Required message to the eNB.By this step, the WT may request the release of the allocated WLANresources. More specifically, the WT Release Required message mayinclude at least one of 1) eNB Xw AP ID, WT Xw AP ID to identify the UE,or 2) cause to release.

Table 8 shows an example of the WT Release Required message. Thismessage is sent by the WT to request the release of all resources for aspecific UE at the WT.

TABLE 8 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES reject ID 9.2.24 by the WT Cause M9.2.4 YES ignore

Referring to Table 8, the WT Release Required message includes eNB Xw APID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP IE”) and cause torelease (“Cause”).

In step S501, the eNB transmits a WT Release Confirm message to the WT.The WT Release Confirm message may include at least one of 1) eNB Xw APID, WT Xw AP ID to identify the UE, or 2) E-RAB ID and DL/UL forwardingGTP tunnel endpoint for E-RABs to be released. The WT initiates releaseof all allocated WLAN resources.

Table 9 shows an example of the WT Release Confirm message. This messageis sent by the eNB to confirm the release of all resources for aspecific UE at the WT.

TABLE 9 IE type and Semantics Assigned IE/Group Name Presence Rangereference description Criticality Criticality Message Type M 9.2.1 YESreject eNB UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the eNBWT UE XwAP ID M UE XwAP Assigned YES ignore ID 9.2.24 by the WT E-RABsto be 0 . . . 1 YES ignore Released List >E-RABs To Be 1 . . . — —Released Item <maxnoof Bearers> >>E-RAB ID M 9.2.18 — — >>DL O GTPTunnel Identifies the — — Forwarding GTP Endpoint Xw transport TunnelEndpoint 9.2.22 bearer used for forwarding of DL PDUs Criticality O9.2.5 YES ignore Diagnostics

Referring to Table 9, the WT Release Confirm message includes eNB Xw APID (“eNB UE XwAP ID”), WT Xw AP ID (“WT UE XwAP IE”) and E-RAB ID andDL/UL forwarding GTP tunnel endpoint for E-RABs to be released (in“E-RABs To Be Release Item”).

If required, in step S502, the eNB may transmit theRRCConnectionReconfiguration message to the UE indicating the release ofWLAN radio resource configuration. In step S503, the UE may reply withRRCConnectionReconfigurationComplete message to the eNB. The UE mayreleases the LWA configuration towards the assigned WLAN resources. TheeNB transmits the UE Context Release message to the WT.

Thereafter, the WT may transmit the SN Status Transfer message to theeNB. This step may be performed for LTE-WLAN integration. Or, the eNBmay perform the path update procedure towards the MME by indicating theE-RABs to be offloaded to the WT. The MME may transmit the Path UpdateAcknowledge message to the eNB. These steps may be performed forLTE-WLAN interworking. It is described above as if procedures forLTE-WLAN aggregation and procedures for LTE-WLAN interworking areseparate from each other. However, it does not have to be separate fromeach other.

FIG. 19 shows another example of a WT initiated WT release procedureaccording to an embodiment of the present invention.

In step S510, the WT transmits the WT Release Required message to theeNB. Step S510 may correspond to step S500 of FIG. 18. The WT ReleaseRequired message may follow Table 8 described above.

In step S511, the eNB transmits the WT Release Confirm message to theWT. Step S511 may correspond to step S501 of FIG. 18. The WT ReleaseConfirm message may follow Table 9 described above.

(6) WT Reconfiguration Notification Procedure

In step S104 of FIG. 10 step S204 of FIG. 12 described above, the eNBmay perform the WT reconfiguration complete procedure by transmittingthe WT Reconfiguration Complete message to the WT.

When the UE cannot connect to the WT, then WT association failurehappens. In order to notify the eNB of WT association failure, a new RRCmessage may be defined according to an embodiment of the presentinvention.

FIG. 20 shows an example of a WT reconfiguration complete procedureaccording to an embodiment of the present invention.

In step S600, the eNB transmits the WT Addition Request message to theWT. In step S601, the WT transmits the WT Addition Request Acknowledgemessage to the eNB. In step S602, the eNB transmits theRRCConnectionReconfiguration message to the UE. In step S603, the eNBtransmits the RRCConnectionReconfigurationComplete message to the UE. Instep S604, the UE starts using the new LWA configuration and performsWLAN association.

Failure of UE connection to the WLAN may happen. In this case, in stepS605, the UE transmits an RRC message with WLAN connection failure. Instep S606, the eNB transmits the WT Reconfiguration Complete messagewith failure cause to the WT. Accordingly, the WT reconfigurationcomplete procedure may be used both for successful case and failurecase. Alternatively, if the eNB judges that something wrong happens withWLAN configuration, the eNB may not trigger the configuration request tothe UE (i.e. step S602), and may transmit the WT ReconfigurationComplete message with failure cause to the WT immediately after stepS601.

FIG. 21 shows an example of a WT release procedure according to anembodiment of the present invention.

In step S610, the eNB transmits the WT Addition Request message to theWT. In step S611, the WT transmits the WT Addition Request Acknowledgemessage to the eNB. In step S612, the eNB transmits theRRCConnectionReconfiguration message to the UE. In step S613, the eNBtransmits the RRCConnectionReconfigurationComplete message to the UE. Instep S614, the UE starts using the new LWA configuration and performsWLAN association.

Failure of UE connection to the WLAN may happen. In this case, in stepS615, the UE transmits an RRC message with WLAN connection failure. Instep S616, the eNB transmits the WT Release Request message with failurecause to the WT. Alternatively, if the eNB judges that something wronghappens with WLAN configuration, the eNB may not trigger theconfiguration request to the UE (i.e. step S612), and may transmit theWT Release Request message with failure cause to the WT immediatelyafter step S611.

In the embodiment of FIG. 20 and FIG. 21, the WT addition procedure wasused as an example. However, the present invention may also be appliedto other procedures such as the WT modification procedure.

FIG. 22 shows a communication system to implement an embodiment of thepresent invention.

An eNB 800 may include a processor 810, a memory 820 and a transceiver830. The processor 810 may be configured to implement proposedfunctions, procedures and/or methods described in this description.Layers of the radio interface protocol may be implemented in theprocessor 810. The memory 820 is operatively coupled with the processor810 and stores a variety of information to operate the processor 810.The transceiver 830 is operatively coupled with the processor 810, andtransmits and/or receives a radio signal. A WT 900 may be connected withthe eNB 800 via Xw interface.

The processors 810 may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Thememories 820 may include read-only memory (ROM), random access memory(RAM), flash memory, memory card, storage medium and/or other storagedevice. The transceivers 830 may include baseband circuitry to processradio frequency signals. When the embodiments are implemented insoftware, the techniques described herein can be implemented withmodules (e.g., procedures, functions, and so on) that perform thefunctions described herein. The modules can be stored in memories 820and executed by processors 810. The memories 820 can be implementedwithin the processors 810 or external to the processors 810 in whichcase those can be communicatively coupled to the processors 810 viavarious means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What is claimed is:
 1. A method for performing, by an eNodeB (eNB), aneNB initiated wireless local area network (WLAN) termination (WT)release procedure in a wireless communication system, the methodcomprising: transmitting a WT Release Request message to a WT via a Xwinterface, wherein the WT is a logical node that terminates the Xwinterface.
 2. The method of claim 1, wherein the WT Release Requestmessage requests the WT to release allocated WLAN resources.
 3. Themethod of claim 1, wherein the WT Release Request message includes atleast one of an eNB Xw application protocol (AP) identifier (ID), a WTUE Xw AP ID, an E-UTRAN radio access bearer (E-RAB) ID and a downlink(DL) or uplink (UL) forwarding GPRS tunneling protocol (GTP) tunnelendpoint for E-RABs to be released or a cause to release.
 4. The methodof claim 1, further comprising transmitting a radio resource control(RRC) connection reconfiguration message to a user equipment (UE). 5.The method of claim 4, further comprising receiving a RRC connectionreconfiguration complete message from the UE.
 6. A method forperforming, by an eNodeB (eNB), a wireless local area network (WLAN)termination (WT) initiated WT release procedure in a wirelesscommunication system, the method comprising: receiving a WT ReleaseRequired message from a WT via a Xw interface; and transmitting a WTRelease Confirm message to the WT via the Xw interface, as a response tothe WT Release Required message, wherein the WT is a logical node thatterminates the Xw interface.
 7. The method of claim 6, wherein the WTRelease Required message requests release of allocated WLAN resources.8. The method of claim 6, wherein the WT Release Required messageincludes at least one of an eNB Xw application protocol (AP) identifier(ID), a WT UE Xw AP ID or a cause to release.
 9. The method of claim 6,wherein the WT Release Confirm message includes at least one of an eNBAP ID, a WT UE Xw AP ID or an E-UTRAN radio access bearer (E-RAB) ID anda downlink (DL) or uplink (UL) forwarding GPRS tunneling protocol (GTP)tunnel endpoint for E-RABs to be released.
 10. A method for performing,by an eNodeB (eNB), a wireless local area network (WLAN) termination(WT) reconfiguration notification procedure in a wireless communicationsystem, the method comprising: receiving a radio resource control (RRC)message which indicates a WLAN connection failure from a user equipment(UE); and transmitting a failure cause corresponding the WLAN connectionfailure to a WT via a WT interface, wherein the WT is a logical nodethat terminates the Xw interface.
 11. The method of claim 10, whereinthe failure cause is transmitted via a WT Reconfiguration Completemessage.
 12. The method of claim 10, wherein the failure cause istransmitted via a WT Release Request message.
 13. The method of claim10, wherein the failure cause is transmitted immediately after receivinga WT Addition Request Acknowledge message from the WT.